Inverter Unit

Abstract

To provide an inverter unit for a compressor of a vehicle air conditioning unit with an arrangement for increasing a creepage distance.SOLUTION: In an electric compressor 1000 of a vehicle air conditioning system, an inverter unit 100 includes an inverter 110, an inverter housing 120, and an insulating member. The inverter 110 drives an electric motor 200, and includes at least one power module that converts high voltage (HV) direct current (DC) to three-phase alternating current (AC) that drives the electric motor 200. The inverter housing 120 receives the inverter 110, and the power module 112 is attached to an end wall 120a of the inverter housing 120 by bolts. An insulating member corresponding to each bolt is arranged between the head of a corresponding bolt and the power module.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an inverter unit, and more specifically, to an inverter unit for a compressor of a vehicle air conditioning unit.

Background Art

[0002] Generally, an electric compressor for a vehicle air conditioning system includes a compression unit for compressing a refrigerant, an electric motor for driving the compression unit, and an inverter unit. This electric compressor further includes a main housing, also called a compressor housing, that houses the compression unit and the electric motor, and a separate inverter housing that houses the inverter unit. This compressor housing is made of a metal such as aluminum and is generally grounded.

[0003] The inverter housing is also made of a metal such as aluminum and includes an end wall, a peripheral wall extending from the outer periphery of the end wall and defining a printed circuit board (PCB) accommodation space, and an open end of the inverter housing that can be closed by a removable cover. The inverter housing is connected to the compressor housing and is grounded either directly or via the compressor housing. The inverter unit includes an inverter composed of a printed circuit board hereinafter referred to as a PCB, and a power module received inside the inverter housing. The PCB and the power module are functionally coupled to an electric motor received in the main housing to drive the electric motor in a controlled manner. Specifically, the PCB accommodation space is arranged adjacent to the electric motor receiving portion of the main housing when the inverter housing is assembled to the main housing. The power module generates heat during its operation. This heat generation may cause melting of important elements of the power module, damage or failure of the power module due to a decrease in the mechanical strength of important elements of the power module at high temperatures. In order to prevent problems caused by such heat generation of the power module, it is required to dissipate heat from the power module in order to prevent damage and failure of the power module and ensure efficient performance of the power module. The power module is pressed against the end wall of the inverter housing, and the refrigerant received in the electric motor accommodation space of the main housing contacts the end wall, thereby taking heat from the end wall and dissipating heat from the power module. The PCB includes a plurality of electronic components for performing inverter operation and electric motor control in various modes by providing a controlled input to the electric motor. The cover of the inverter housing is also made of a metal material.

[0004] Referring to FIG. 1 of the accompanying drawings, a power module 2 held inside an inverter housing and attached to an end wall 4 of the inverter housing is illustrated. The power module 2 includes a plurality of switching elements molded in a casing of the power module 2. The switching elements include a lead frame 3 that protrudes from the casing of the power module and is connected to a PCB so that DC high-voltage power, low-voltage signals, and AC output can be supplied to corresponding parts within the PCB. Accordingly, a part of the lead frame 3 can be a high-voltage portion. The power module 2 is attached to and press-fitted against the end wall 4 of the inverter housing by a metal bolt 6 and a metal washer 8. The bolt 6 is a threaded bolt including a threaded shaft portion 6a and a bolt head 6b. The bolt head 6b, together with the washer 8, presses the power module 2 against the end wall 4 of the inverter housing by engaging the threaded shaft portion 6a with the end wall 4. More specifically, the washer 8 includes a hole 8a through which the threaded shaft portion 6a passes, while the bolt head 6b rests on the washer 8. The casing of the power module 2 includes a through hole 2b through which the threaded shaft portion 6a passes. The threaded shaft portion 6a of the bolt 6 passes through the holes 8a and 2b formed in the washer 8 and the power module 2, respectively, and engages with a blind hole formed in the end wall 4. When the threaded shaft portion 6a engages with the blind hole in the end wall 4, the washer 8 and the power module 2 are disposed between the bolt head 6b and the end wall 4. As a result, the power module 2 is fixed to the end wall 4 of the inverter housing by tightening the bolt 6. With such a configuration, the power module 2 is maintained in sufficient contact with the end wall 4 for improved heat dissipation. In particular, with such a configuration, the power module 2 is pressed against the end wall 4 to address insulation problems caused by the gap between the power module 2 and the end wall 4.

[0005] A washer 8 is disposed between the bolt head 6b and the power module 2. With the screw shaft portion 6a engaged with the end wall 4, the power module 2 is surely pressed against the end wall 4 by the bolt head 6b without being scratched / damaged by the bolt head 6b. Generally, the washer 8 is used to protect the power module 2 from damage by the bolt head 6b during the screwing of the bolt 6 into the end wall 4. Further, the illustrated power module 2 includes a dummy frame disposed in the casing for relaying the conductive connection between some lead frames and switching elements. A part of the end of the dummy frame remains exposed from one side surface of the casing. The exposed portion 2a of the dummy frame is not connected to any electrical component and functions as a high-voltage portion. If the creepage distance between the high-voltage portions 2a, 3 and other conductive / grounding elements is insufficient, it may cause a short circuit. The creepage distance is the length of the shortest path that the current travels until it reaches the conductive / grounding element. In the case of the conventional mounting method of attaching the power module 2 to the end wall 4, the end wall 4 of the inverter housing is grounded, the bolt 6 is screwed into engagement with the end wall 4, and the metal washer 8 is in contact with the bolt head 6b of the metal bolt 6. Therefore, the washer 8 is also conductively connected to the ground via the bolt 6. In such a scenario, the washer 8 acts as a conductive element that may cause a short circuit between the washer 8 and the high-voltage portions 2a, 3 because the creepage distance between the washer 8 and the high-voltage portions 2a, 3 is not sufficient. FIG. 1 depicts the creepage distance "d" between the high-voltage elements 2a, 3 and the washer 8. The creepage distance is measured from the outer peripheral portion of the washer 8 and the nearest high-voltage portion 2a, 3. The requirement for the creepage distance "d" is much shorter than the requirement for the air distance. The problem of short circuit due to the insufficient creepage distance "d" between the high-voltage elements 2a, 3 and the washer 8 of the power module 2 deteriorates when the high-voltage elements 2a, 3 are exposed from at least one side of the power module 2. If the washer 8 is not disposed between the bolt head 6b and the power module 2, there is a risk of short circuit between the high-voltage (HV) element 2a of the power module 2 and the bolt head 6b.

[0006] Therefore, in the conventional arrangement, it is not possible to provide a sufficient creepage distance "d" between the high-voltage (HV) portion of the power module 2 and the washer 8 and / or the bolt head 6b, thereby causing problems. More specifically, in the case of the conventional configuration, the creepage distance "d" between the high-voltage (HV) element 2a of the power module 2 and the washer 8 and / or the bolt head 6b is below the standard safety requirements for the efficient and safe operation of the power module 2.

[0007] Therefore, there is a need for an inverter unit configured with an arrangement for increasing the creepage distance between the high-voltage element of the power module and the washer and / or bolt head for attaching the power module to the end wall of the inverter housing.

Summary of the Invention

Problems to be Solved by the Invention

[0008] The main object of the present invention is to provide an inverter unit configured with an arrangement that solves the problem of insufficient creepage distance between important elements of the inverter unit, which was a problem with conventional inverter units.

[0009] Another object of the present invention is to provide an inverter unit in which the power module is mounted on the end wall of the inverter housing and pressed against the end wall, thereby achieving efficient heat dissipation from the power module to the refrigerant in the main housing in contact with the end wall.

[0010] Yet another object of the present invention is to provide an inverter unit that is convenient to assemble.

[0011] In this specification, some elements or parameters may be indexed, for example, as a first element, a second element, and the like. In this case, unless otherwise specified, this indexing is only intended to distinguish and name similar but not identical elements. Since these terms can be converted without departing from the present invention, no precedence concept should be inferred from such indexing. Furthermore, this indexing does not imply any order in the installation or use of the elements of the present invention.

Means for Solving the Problems

[0012] Disclosed is an inverter unit according to an embodiment of the present invention. The inverter unit includes an inverter, an inverter housing, and an insulating member. The inverter includes at least one power module that drives an electric motor and converts high-voltage (HV) direct current (DC) into three-phase alternating current (AC) for driving the electric motor. The inverter housing receives the inverter. The power module is attached to an end wall of the inverter housing by bolts. An insulating member corresponding to each bolt is disposed between the head of the bolt and the power module.

[0013] Generally, the end wall defines a closed end of the inverter housing in which holes are formed to constitute screw engagement with the corresponding bolts.

[0014] Preferably, the insulating member includes a base portion. The power module is securely attached to the end wall of the inverter housing and the base portion by the bolts. The threaded shaft portion of the bolt axially penetrates through a hole formed in the base portion and a through portion provided in the power module to engage with the end wall. The head of the bolt stays above the base portion such that the base portion is disposed between the head of the bolt and the power module to separate the head of the bolt from the power module.

[0015] Specifically, the base portion of the insulating member has a radius dimension larger than the radius dimension of the head of the bolt, and defines an annular space therebetween.

[0016] Generally, the hole is disposed centrally with respect to the base portion.

[0017] Furthermore, the insulating member includes a side wall that extends axially from the base portion and away from the power module to increase the creepage distance between the head of the bolt and the high-voltage element of the power module.

[0018] Furthermore, the side wall of the insulating member has a height of at least twice the height of the head of the bolt.

[0019] According to another embodiment of the present invention, at least one of the insulating members is overmolded with the corresponding bolt and integrally formed.

[0020] According to one embodiment of the present invention, the side wall has a uniform height along the peripheral edge of the base portion.

[0021] According to another embodiment of the present invention, at least a part of the side wall of the insulating member is inclined with respect to the central axis "C".

[0022] Furthermore, at least one of the inner surface and the outer surface of the side wall is a concavo-convex surface.

[0023] Generally, the insulating member has a hollow structure with a circular cross-section.

[0024] Furthermore, the inverter of the inverter unit includes a separator disposed between a printed circuit board (PCB), the power module, and a removable cover.

[0025] Generally, a plurality of electronic components are mounted on the PCB, and the separator separates the electronic components.

[0026] Also, the power module is connected to the PCB via pins protruding from the PCB.

[0027] Generally, the PCB and the separator include corresponding first openings and second openings for passing through the insulating member therein.

[0028] According to another embodiment of the present invention, the separator includes the insulating member integrally formed with the separator.

[0029] Furthermore, the bolt is deployed using a deployment tool selected from the group including a driver and an Allen key.

[0030] Also disclosed is an electric compressor according to an embodiment of the present invention. The electric compressor includes a compression unit, an electric motor, and an inverter unit. The compression unit compresses fluid. The electric motor drives the compression unit. The inverter unit disclosed above drives the electric motor.

[0031] Other features, details, and advantages of the present invention can be inferred from the following description of the invention. A more complete understanding of the present invention and its attendant advantages will be readily obtained by referring to the following detailed description when considered in conjunction with the accompanying drawings, as the present invention will be better understood.

Brief Description of the Drawings

[0032]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6a

Figure 6b

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Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Best Mode for Carrying Out the Invention

[0033] In the figures, the present invention is disclosed in sufficient detail to be practicable, and it should be noted that the figures serve to better define the present invention as needed. However, the present invention should not be limited to the embodiments disclosed herein.

[0034] The present invention will be described by taking an inverter unit of an electric compressor for a vehicle air conditioning system as an example. However, the present invention is also applicable to any electronic system used in vehicle and non-vehicle applications.

[0035] FIG. 2 is a schematic diagram of an electric compressor 1000 of a vehicle air conditioning system according to an embodiment of the present invention. The electric compressor 1000 includes an inverter unit 100, an electric motor 200, and a compression unit 300 that is driven by the electric motor 200 to compress refrigerant. The electric compressor 1000 further includes a main housing, also called a compressor housing 210, and a separate inverter housing 120. The main housing or compressor housing 210 houses the electric motor 200 and the compression unit 300. The inverter housing 120 houses the inverter 110. The compressor housing 210 is made of a metal such as aluminum and is generally grounded to the vehicle via a mounting portion (not shown).

[0036] The inverter housing 120 includes an end wall 120a and a peripheral wall 120b extending from the peripheral edge of the end wall 120a and defining a PCB accommodation space and an open end of the inverter housing 120. The inverter housing 120 is connected to the main housing 210 and grounded via the compressor housing 210. The open end of the inverter housing 120 can be closed by a detachable cover 120c. The inverter 110 is functionally coupled to the motor 200 received in the main housing 210 to drive the motor 200 in a controlled manner. Specifically, when the inverter housing 120 is assembled to the main housing 210 and the inverter 110 is functionally connected to the motor 200 by an electrical connection interface 220 provided through the end wall 120a, the PCB accommodation space is disposed adjacent to the motor receiving portion of the main housing 210. With such a configuration in which the PCB accommodation space and the motor receiving portion of the main housing 210 are disposed adjacent to each other, the cooling fluid, particularly the refrigerant received in the motor receiving portion, also cools the end wall 120a, which is because the end wall 120a of the inverter housing 120 is in contact with the main housing 210 cooled by the refrigerant.

[0037] FIG. 3 of the accompanying drawings shows an exploded view of an inverter unit 100 according to an embodiment. The inverter unit 100 includes an inverter housing 120 and an inverter 110 received in the inverter housing 120. The inverter 110 includes at least one power module 112 and a PCB 116 including a plurality of electronic components disposed thereon. Further, the inverter unit 100 includes a high voltage (HV) connector 230 and a low voltage (LV) connector 240, both of which are provided on the end wall 120a of the inverter housing 120 to receive a high voltage power supply and a control signal from a vehicle system. The inverter 110 drives the motor 200 and includes a power module 112 that converts high voltage (HV) direct current (DC) into three-phase alternating current (AC) for driving the motor 200.

[0038] FIG. 4 is a cross-sectional view along a cutting plane passing through one of the bolts 114, depicting the assembled state of the power module 112, the insulating member 130, and the bolt 114. As depicted in FIG. 4, the power module 112 is attached to the end wall 120a of the inverter housing 120. The end wall 120a of the inverter housing 120 is formed with a hole 122a for receiving the corresponding threaded portion 114b of the bolt 114 and constituting a threaded engagement therewith. In one embodiment, the hole 122a is a non-through hole without threads, and the bolt 114 is a self-tapping bolt that forms threads in the hole 112a as the bolt is deployed. Alternatively, the hole 112a is a threaded hole, and the bolt 114 is screwed into the threaded hole 112a to press the power module 112 against the end wall 120a of the inverter housing 120, thereby improving the surface contact between the power module 112 and the end wall 120a and promoting heat dissipation from the power module 112. The bolt 114 is deployed using a deployment tool selected from the group consisting of a driver, an Allen key, or other devices that can operate in the limited space around the bolt head. Further, in the present invention, the insulating member 130 is disposed between the power module 112 and the bolt head 114a of the bolt 114.

[0039] FIG. 5 is an isometric view of a power module 112 according to an embodiment. The power module 112 includes a casing 112d having a rectangular parallelepiped shape. The casing 112d is made of a non-conductive material such as resin. A plurality of switching elements are disposed inside the casing 112d of the power module 112 and covered. Specifically, the switching elements are molded in a resin casing 112d. A plurality of lead frames or pins 112b for conducting connection of the switching elements extend out of the casing 112d from opposite long sides of the rectangular casing 112d. The lead frames or pins 112b are made of a conductive material such as copper. According to an embodiment depicted in FIG. 5, six lead frames 112b extend from a first long side of the casing 112d, and twenty lead frames or pins 112b extend from a second long side of the casing 112d, and the second long side faces the first long side. The lead frames or pins 112b are bent at a right angle so as to be connectable to a PCB 116. High-voltage power from an in-vehicle battery is supplied to the switching elements through a part of the lead frames or pins 112b. A further control signal is supplied to the switching elements through the other of the lead frames or pins 112b, and thus, the power module 112 can convert direct current (DC) to alternating current (AC). The lead frames or pins 112b to which high-voltage power is supplied from the battery can be high-voltage portions.

[0040] Referring back to FIG. 5, the casing 112d of the power module 112 further includes notches 112c, formed on both opposing short sides thereof, as insertion portions for passing bolts 114 for attaching the power module 112 to the end wall 120a therethrough. Generally, the notches 112c are disposed at the center of the short sides of the casing 112d. In another example, the insertion portion can also be formed by a hole passing through the power module. Further, in the present embodiment, a dummy frame is provided on the casing 112d to relay the conductive connection between a part of the lead frame or pins 112b and the switching element. A part of the end of the dummy frame remains exposed from the short sides of the casing 112d of the power module 112 and functions as the high-voltage portion 112a. The exposed portion of the dummy frame is not connected to any of the electrical components, but they can also be the high-voltage portion 112a. Also, the lead frame and pins 112b can also be regarded as high-voltage elements.

[0041] FIGS. 6A and 6B depict an insulating member 130 of one embodiment. The insulating member 130 includes a base 130a having a uniform thickness "t1". A hole 132a is formed at the center of the base 130a. Preferably, the insulating member 130 is a cylindrical element having one closed end and an open end on the opposite side. Specifically, the insulating member 130 is in the form of a cup including the base 130a and a side wall 130b extending from the base 130a. The side wall 130b has a thickness "t2". The insulating member 130 is made of a non-conductive material such as resin.

[0042] According to another embodiment of the present invention, as shown in FIG. 7, at least one of the insulating members 130 is overmolded with the corresponding bolt 114 and integrally formed. In such a configuration, the bolt head 114a stays above the base 130a of the insulating member 130, while the threaded shaft portion 114b of the bolt 114 hangs down from the base 130a of the insulating member 130. With such a configuration, when the bolt 114 is deployed, the insulating member 130 rotates together with the bolt 114 and engages with the hole 122a formed in the end wall 120a.

[0043] As described above, the power module 112 is attached to the end wall 120a of the inverter housing 120 by bolts 114. Further, the insulating member 130 is disposed between the power module 112 and the bolt head 114a of the bolt 114 when the bolt 114 engages with the end wall 120a in order to attach the power module 112 to the end wall 120a and press the power module 112 against the end wall 120a. In particular, the power module 112 is securely attached to the end wall 120a by bolts 114 such that the base 130a is on one side of the power module 112 and the end wall 120a of the inverter housing 120 is on the other side of the power module 112. Specifically, the threaded shaft portion 114b of the bolt 114 axially penetrates the hole 132a of the base 130a and the notch 112c provided in the power module 112 and engages with the end wall 120a, but the head 114a of the bolt 114 remains above the base 130a. Since the base 130a is disposed between the bolt head 114a of the bolt 114 and the power module 112, the bolt head 114a of the bolt 114 and the power module 112 do not contact each other. In this example, two bolts 114 attach opposite surfaces of the power module 112 to the end wall 120a of the inverter housing 120. However, the present invention is not limited to any specific number or arrangement of bolts as long as a corresponding insulating member 130 is disposed between the bolt head 114a of each bolt 114 and the power module 112.

[0044] As described in the background art, the bolt 114 is engaged with the grounded end wall 120a. If the component disposed between the bolt head 114a and the power module 112 were a metal washer 8 as in the conventional configuration, the creepage distance to be considered would be the distance between the high-voltage portion of the power module and the outer peripheral portion of the metal washer that contacts the head 114a of the bolt 114. However, in the case of the mounting configuration of the inverter unit 100 composed of insulating elements, the creepage distance "D" between the high-voltage portion 112a of the power module 112 and the bolt head 114a becomes large due to the peculiar cup-shaped configuration of the insulating member 130.

[0045] FIG. 8 shows a schematic view of the mounting configuration of the inverter unit 100 configured using the insulating member 130. Also shown is an enlarged view depicting the creepage distance "D" between the bolt head 114a and the high-voltage portion 112a of the power module 112. As depicted, the creepage distance D is calculated as the sum of all distances between the high-voltage portion 112a and the bolt head 114a. In particular, the creepage distance is the distance "x" from the high-voltage portion 112a to the insulating member 130 along the outer surface of the power module 112, and the length of the path traced from the point where the current exits the power module 112 from the outside, along the inner and outer surfaces of the insulating member 130 to the bolt head 114a. The length of the path traced by the current to reach the bolt head 114a from outside the power module 112 is the first thickness "t1" of the base 130a, also referred to as the base 130a, and the length of the portion of the path along the outer surface of the side wall 130b that is equal to the height "H" of the side wall 130b, and the second thickness "t2" of the side wall 130b, and also the length of the portion of the path along the inner surface of the side wall 130b that is equal to the height "H" of the side wall 130b, including the distance between the inner surface of the side wall 130b and the bolt head 114a. In particular, the creepage distance is measured as follows. D = x + t1 + H + t2 + H + y In the case of the mounting configuration of the inverter unit 100 of the present invention using the insulating member 130, the creepage distance D is greater than the creepage distance d in the case of the mounting configuration of the conventional inverter unit without using the insulating member, and D >> d. A fillet is formed at the interface between the base 130a and the side wall 130b.

[0046] In the case of the inverter unit 100 of the present invention, in the case of the power module 112 where the dummy frame is exposed at the end on the short side of the casing 112d, the creepage distance "D" is calculated from the high-voltage portion 112a to the bolt head 114a along the side wall 130b of the insulating member 130. As shown in FIG. 8 and described in the description of FIG. 8, the creepage distance "D" includes the length of the current flow path along the inner and outer surfaces of the insulating member 130, and is greater than the creepage distance "d" between the high-voltage portion of the power module and the outer peripheral portion of the washer 8 of the conventional inverter unit shown in FIG. 1.

[0047] In the configuration of a conventional inverter unit in which a washer is disposed between the bolt head and the end wall, it has been difficult to secure a sufficient creepage distance. However, in the present invention, the component disposed between the head 114a of the bolt 114 and the power module 112 is the insulating member 130. Since the insulating member 130 is a non-conductive component, the creepage distance is the distance from the high-voltage portions 112a, 112b to the free surface of the power module 112 and the distance that the current must traverse along the surface of the insulating member 130 in order to reach the bolt head 114a.

[0048] The creepage distance "D" between the high-voltage portion 112a of the power module 112 and the bolt head 114a can be increased by changing the insulating element 130. For example, the corresponding bolt 114 for attaching the power module 112 to the end wall 120a of the inverter housing 120 includes a bolt head 114a and a threaded shaft portion 114b. The diameter of the base 130a or the inner diameter of the hollow cylinder defined by the side wall 130b of the insulating element 130 is larger than the diameter of the bolt head 114a and surrounds the bolt head 114a to define an annular space therebetween. The annular space between the bolt head 114a and the inner diameter of the hollow cylinder defined by the side wall 130b is directly related to the creepage distance. More specifically, the creepage distance increases with the annular interval between the bolt head 114a and the inner diameter of the hollow cylinder defining the side wall 130b. The height of the side wall 130b of the insulating member 130 is at least twice the height of the bolt head 114a. Referring again to FIG. 4 of the accompanying drawings, if the height of the side wall 130b is represented by "H" and the height of the bolt head 114a is represented by "h", then H = 4h. The height difference between the side wall 130b of the insulating member 130 and the bolt head 114a of the bolt 114 is directly related to the creepage distance. More specifically, the creepage distance increases with the increase in the height difference between the side wall 130b and the bolt head 114a. The side wall can have different configurations to increase the creepage distance. According to one embodiment, the side wall 30b has a uniform height along the peripheral edge of the base 130a. According to another embodiment, at least a part of the side wall 130b of the insulating member 130 is inclined with respect to the central axis "C" to increase the creepage distance between the high-voltage portion 112a of the power module 112 and the bolt head 114a. In one embodiment, both the inner and outer surfaces of the side wall 130b are smooth surfaces.

[0049] Referring to FIGS. 9 and 10, a configuration for attaching the power module 112 to the end wall 120a by bolts 114 and corresponding insulating members 130 is depicted. More specifically, the threaded shaft portion 114b of the bolt 114 axially penetrates a hole 132a formed in the base 130a of the insulating member 130 and engages with a hole 122a formed in the end wall 120a, while the bolt head 114a remains above the base 130a. The threaded shaft portion 114b of the bolt 114 penetrates through respective notches 112c formed in the power module 112 and is received in corresponding holes 122a formed in the end wall 120a to attach the power module 112 to the end wall 120a. More specifically, the end wall 120a of the inverter housing 120 is formed with holes 122a for receiving the corresponding bolts 114 to constitute a screw engagement. Further, such a configuration of attaching the power module 112 onto the end wall 120a of the inverter housing using the bolts 114 results in pressing the power module 112 against the end wall 120a and improving the heat dissipation from the power module 112. Such a configuration addresses insulation problems caused by any air gaps between the power module 112 and the end wall 120a. The base 130a further provides sufficient support and surface contact against the bolt head 114a, thereby improving the screw engagement of the bolt 114 with the end wall 120a.

[0050] FIG. 9 is an exploded perspective view showing the assembly of the power module 112, the insulating member 130, and the bolts 114 along the end wall 120a of the inverter housing 120. To further improve the surface contact between the power modules 112 and improve the heat dissipation from the power modules, the end wall 120a includes a flat platform 122b formed thereon. FIG. 9 also shows an enlarged view depicting the flat platform 122b formed on the end wall 120a. The holes 122a for receiving and engaging the bolts 114 are arranged along the periphery of the flat platform 122b, particularly on both opposite short sides thereof. The flat platform 122b is complementary in shape and size to the power module 112 and enhances the surface contact between the end wall 120a and the power module 112. Generally, a gap filler 124 is disposed between the power module 112 and the flat platform 122b to further improve the surface contact between the power module 112 and the end wall 120a and improve the heat dissipation of the power module 112 when the power module 112 is mounted on the flat platform 122b using the bolts 114. In particular, the gap filler 124 fills small gaps such as gaps caused by roughness and geometric defects of the power module 112 and the end wall 120a. Further, since the gap filler 124 has a better thermal conductivity than air, the gap filler 124 enables improvement of the heat flow between the power module 112 and the end wall 120a. FIG. 10 is a cross-sectional view depicting the assembly of the power module 112, the insulating member 130, and the bolts 114 along a cross-sectional plane passing through both bolts 114. Also depicted is a gap filler 124 disposed between the flat platform 122b formed on the end wall 120a and the lower surface of the power module 112 to increase the surface contact between the power module 112 and the end wall 120a. With such a configuration, as the power module 112 is pressed against the flat platform 122b formed on the end wall 120a by the bolts 114, an improvement in heat dissipation from the power module 112 is achieved. With such a configuration, the surface contact between the power module 112 and the end wall 120a is improved, thereby enhancing the heat dissipation.More specifically, the heat generated in the power module 112 can be efficiently released to the refrigerant on the other side portion of the end wall 120a. According to one embodiment, a groove 122d is provided between the hole 122a and the corresponding short side of the flat platform 122b to accommodate an extra gap filler that is pushed outwards when the power module 112 is pressed against the flat platform 122b by the bolt 114.

[0051] The inverter 110 further includes a separator 118 disposed between the power module 112 and the removable cover 120c. FIG. 3 shows the relative positions and orders of the PCB 116 and the separator 118 with respect to the insulating member 130 when assembled with each other. FIG. 11 is an isometric view of the PCB 116 for the inverter 110. The PCB 116 also includes a plurality of mounted electronic components 116a (not shown in FIG. 11). The separator 118 shown in FIG. 12 separates these electronic components 116a mounted on the PCB 116. FIG. 12 is an isometric view of the separator for the inverter 110. The separator 118 is a plastic material and provides insulation between various electronic components 116a mounted on the PCB 116, thereby preventing the electronic components from short-circuiting by accidentally contacting each other or due to insufficient spacing between the electronic components 116a. The separator 118 may further include an arrangement configuration for positioning the PCB 116 inside the inverter housing 120. The PCB 116 and the separator 118 include corresponding first openings 116b and second openings 118a for passing through the insulating member 130. The number and arrangement of the first openings 116b on the PCB 116 correspond to the number and spacing of the bolts 114, and more specifically, correspond to the number and spacing of the insulating members 130 corresponding to the bolts 114. Similarly, the number and arrangement of the second openings 118a on the separator 118 correspond to the number and spacing of the bolts 114, and more specifically, correspond to the number and spacing of the insulating members 130 corresponding to the bolts 114. The first opening 116b formed on the PCB 116 and the second opening 118a formed on the separator 118 are aligned with each other so that the insulating member 130 can pass through the first opening 116b and the second opening 118a respectively. After passing through the first opening 116b and the second opening 118a, the insulating member 130 rests on the power module 112, and as the threaded portion 114b of the bolt 114 passes through the corresponding hole 132a formed in the insulating member 130 and engages with the end wall 120a, the power module 112 is pressed against the end wall 120a of the inverter housing 120.The insulating member 130 in the form of a plastic cup further functions as an anti-misassembly function to facilitate the assembly of the power module 112, the separator 118, and the PCB 116 to the end wall 120a of the inverter housing 120.

[0052] FIG. 13 shows an enlarged view of the assembly of the power module 112, the insulating member 130, and the bolts 114 with the PCB 116. Further, FIG. 12 shows the connection between the power module and the PCB 116 via the pins 112b protruding from the power module 112. Referring to FIG. 13, sufficient clearance is provided between the threaded shaft portion 114b of the bolt 114 and the inner wall of the corresponding notch 112c formed on the casing 112d of the power module 112. Further, the outermost end of the lead frame is inserted into the corresponding hole formed in the PCB 116. By such a connection between the pins 112b and the PCB 116, even if there is a clearance between the threaded shaft portion 114b of the bolt 114 and the inner wall of the notch 112c formed on the power module 112, reliable positioning and attachment of the power module 112 to the PCB 116 are achieved. Such a configuration can prevent the threaded shaft portion 114b of the bolt 114 from contacting the inner wall of the corresponding notch 112c of the power module 112, thereby avoiding the shortening of the creepage distance through the contact portion. Further, with such a configuration, the power module 112 can move in the axial direction of the deployment of the bolt 114, and the power module 112 can be reliably attached to the desired axial position with respect to the PCB 116. More specifically, with such a configuration, the lateral relative movement of the power module 112 with respect to the PCB 116 is blocked, but when the bolt is deployed to press the power module 112 against the end wall 120a, the relative movement along the axial direction of the movement of the bolt 114 is allowed.

[0053] According to another embodiment shown in FIG. 14, at least one of the inner and outer surfaces of the side wall 130b is an uneven surface. In particular, serrations 132b are provided to increase the creepage distance between the high-voltage portion 112a of the power module 112 and the bolt head 114a. Although the serrations 132b are depicted on the inner surface of the side wall 130b in FIG. 13, the serrations 132b can also be configured on the outer surface of the side wall 130b.

[0054] However, the present invention is not limited to the specific shape, configuration, number, arrangement of the insulating member, the configuration of the side wall 130b, the annular space between the side walls of the bolt, the height of the side wall with respect to the bolt head, and the position of the hole in the base portion through which the bolt passes.

[0055] According to yet another embodiment illustrated in FIG. 15, the separator 118 includes an insulating member 118b formed integrally with the separator 118. In such a configuration, the insulating member 118b penetrates through the first opening 116b, and as the separator 118 is placed on the power module 112 and the threaded portion 114b of the bolt 114 passes through the hole 118a formed in the insulating member 118 and engages with the end wall 120a, the power module 112 is pressed against the end wall 120a of the inverter housing 120. More specifically, the separator 118 includes a lip portion 118c extending parallel to the power module 112. With such a configuration, the creepage distance between the high-voltage portion 112a of the power module 112 and the bolt head 114a is further increased because the current emitted from the high-voltage portion 112a of the power module 112 must follow the creepage path "P" along the surfaces of the separator 118 and the insulating member 118b formed integrally with the separator 118 to reach the bolt head 114a.

[0056] Also disclosed is an electric compressor 1000 according to an embodiment of the present invention. Referring again to FIG. 2, the electric compressor 1000 includes a compression unit 300, an electric motor 200, and an inverter unit 100. The compression unit 300 compresses a fluid, particularly a refrigerant, before the refrigerant is supplied to the condenser of the air conditioning loop. The electric motor 200 drives the compression unit 300. The inverter unit 100 disclosed above drives the electric motor 200.

[0057] Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. Accordingly, it is to be understood that the invention can be practiced otherwise than as specifically described herein.

[0058] In any case, since there may be other embodiments, the present invention should not be limited to, nor should it be intended to be limited to, the embodiments specifically described herein. The present invention extends to any equivalent means and combinations of technically operative means.

Explanation of Signs

[0059] 100 Inverter unit 110 Inverter 112 Power module 112d Casing 114 Bolt 114b Threaded portion 116 PCB 116b First opening 118 Separator 118a Second opening 118c Lip portion 120 Inverter housing 120a End wall 122a, 132a Hole 130 Insulating member 130a Base 130b Side wall 230 High voltage (HV) connector 240 Low voltage (LV) connector 200 Electric motor

Claims

1. An inverter unit (100), comprising: An inverter (110) for driving an electric motor (200), the inverter (110) including at least one power module (112) for converting high voltage (HV) direct current (DC) into three-phase alternating current (AC) for driving the electric motor (200); An inverter housing (120) for receiving the inverter (110); The power module (112) is adapted to be attached to an end wall (120a) of the inverter housing (120) by bolts (114), and an insulating member (130, 118b) made of a non-conductive material is disposed between a head (114a) of the bolt (114) and the power module (112); The insulating member (130) includes a base portion (130a), the power module (112) is securely attached to the base portion (130a) and the end wall (120a) of the inverter housing (120) by the bolt (114), a threaded shaft portion (114b) of the bolt (114) axially penetrates through a hole (132a) formed in the base portion (130a) and a through portion (112c) provided in the power module (112) and engages with the end wall (120a), while the head (114a) of the bolt (114) remains on the base portion (130a), and the base portion (130a) is disposed between the head (114a) of the bolt (114) and the power module (112) to separate them; The insulating member (130) further includes a side wall (130b) extending axially from the base portion (130a) and away from the power module, and the inverter unit (100) is characterized in that it is in the form of a cup.

2. The end wall (120a) defines a closed end of the inverter housing (120) in which a hole (122a) is formed, and constitutes a threaded engagement with the corresponding bolt (114). The inverter unit (100) according to Claim 1.

3. The base portion (130a) of the insulating member (130) has a radius dimension larger than a radius dimension of the head (114a) of the bolt (114), and defines an annular space therebetween. The inverter unit (100) according to Claim 1.

4. The inverter unit (100) according to claim 1, wherein the hole (132a) is disposed at the center with respect to the base portion (130a).

5. The inverter unit (100) according to claim 1, wherein the side wall (130b) of the insulating member (130) has a height that is at least twice the height of the head (114a) of the bolt (114).

6. The inverter unit (100) according to claim 1, wherein the side wall (130b) has a uniform height along the peripheral edge of the base portion (130a).

7. The inverter unit (100) according to claim 1, wherein at least a part of the side wall (130b) of the insulating member (130) is inclined with respect to the central axis "C".

8. The inverter unit (100) according to claim 1, wherein at least one of the inner surface and the outer surface of the side wall (130b) is a concavo-convex surface.

9. The inverter unit (100) according to claim 1, wherein the insulating member (130) has a hollow configuration with a circular cross-section.

10. The inverter unit (100) according to claim 1, wherein at least one of the insulating members (130) is overmolded with the corresponding bolt (114) and integrally formed.

11. The inverter unit (100) according to claim 1, wherein the inverter (100) further includes a printed circuit board (PCB) (116) and a separator (118) disposed between the power module (112) and a removable cover (120c).

12. The inverter unit (100) according to claim 11, wherein the printed circuit board (PCB) (116) and the separator (118) each include a corresponding first opening (116b) and a second opening (118a) for penetrating the insulating member (130).

13. The inverter unit (100) according to claim 11, wherein the separator (118) includes the insulating member (118b) integrally formed with the separator (118).

14. An electric compressor (1000), a compression unit (300) adapted to compress a fluid, an electric motor (200) for driving the compression unit (300), the inverter unit (100) according to claim 1, A motor compressor (1000) comprising an inverter unit (100) adapted to drive the electric motor (200).

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